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	 <P ALIGN="CENTER" CLASS="page_heading">Errors reported by CheckUpDown</P> 
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			 <P><B>Introduction to errors</B></P> 
			 <P>Any client (e.g. your Web browser or our CheckUpDown robot) goes
				through the following cycle when it communicates with your Web server:</P> 
			 <UL> 
				<LI>Obtain an IP address from the IP name of your site (your site
				  URL without the leading 'http://'). This lookup (conversion of IP name to IP
				  address) is provided by domain name servers (DNSs). </LI> 
				<LI>Open an IP socket connection to that IP address. </LI> 
				<LI>Write an HTTP data stream through that socket. </LI> 
				<LI>Receive an HTTP data stream back from your Web server in
				  response. This data stream contains status codes whose values are determined by
				  the HTTP protocol. Parse this data stream for status codes and other useful
				  information. </LI> 
			 </UL> 
			 <P>An error may occur in any of the above steps. Our CheckUpdown
				robot isolates any error and reports it as an error code for your account (as a
				clickable link) along with details of when the error was detected.</P> 
			 <P>The error codes the client may receive are given below - follow
				the URL for each to see further discussion of the error and what further action
				we recommend.</P> 
			 <P><B>0?? errors</B></P> 
			 <P>Errors with a code in the range 001-099 indicate a fundamental
				failure to communicate, typically in the early steps above. Note these errors
				are not defined in the HTTP protocol - they are specific to our CheckUpDown
				service.</P> 
			 <P><A HREF="E001.html">001 - Unknown Host</A><BR> <A
				HREF="E002.html">002 - I/O Exception</A><BR> <A HREF="E003.html">003 -
				Undefined HTTP Status Code</A><BR> <A HREF="E004.html">004 - Bad URL</A><BR>
				<A HREF="E005.html">005 - Host not reachable</A><BR> <A HREF="E006.html">006 -
				No connection</A><BR> <A HREF="E007.html">007 - I/O Interrupt</A><BR>
				<A HREF="E008.html">008 - Socket failure</A><BR> <A HREF="E009.html">009 - SSL
				secure socket failure</A><BR> <A HREF="E010.html">010 - Check word not
				found</A><BR><A HREF="E011.html">011 - Socket Timeout</A></P> 
			 <P><B>3?? errors</B></P> 
			 <P>Errors with a code in the range 300-399 indicate a redirection of
				your Web site URL. As of September 2000, CheckUpDown follows some URL
				redirections (301, 302, 303, 307) automatically, so these should no longer be
				reported as an error.</P> 
			 <P><A HREF="E300.html">300 - Multiple Choices</A><BR>
				<A HREF="E301.html">301 - Moved permanently</A><BR> <A HREF="E302.html">302 -
				Moved temporarily</A><BR> <A HREF="E303.html">303 - See other</A><BR>
				<A HREF="E304.html">304 - Not modified</A><BR> <A HREF="E305.html">305 - Use
				proxy</A><BR> <A HREF="E307.html">307 - Temporary Redirect</A><BR> </P> 
			 <P><B>4?? errors</B></P> 
			 <P>Errors with a code in the range 400-499 occur where your Web
				server - incorrectly or not - dislikes the HTTP data streams that the client
				sends to it. Quite rare.</P> 
			 <P><A HREF="E400.html">400 - Bad request</A><BR> <A
				HREF="E401.html">401 - Unauthorized</A><BR> <A HREF="E403.html">403 -
				Forbidden</A><BR> <A HREF="E404.html">404 - Not found</A><BR>
				<A HREF="E405.html">405 - Method not allowed</A><BR> <A HREF="E406.html">406 -
				Not acceptable</A><BR> <A HREF="E407.html">407 - Proxy authentication
				required</A><BR> <A HREF="E408.html">408 - Request timeout</A><BR>
				<A HREF="E409.html">409 - Conflict</A><BR> <A HREF="E410.html">410 -
				Gone</A><BR> <A HREF="E411.html">411 - Length required</A><BR>
				<A HREF="E412.html">412 - Precondition failed</A><BR> <A HREF="E413.html">413 -
				Request entity too large</A><BR> <A HREF="E414.html">414 - Request URI too
				long</A><BR> <A HREF="E415.html">415 - Unsupported media type</A><BR>
				<A HREF="E416.html">416 - Requested Range not satisfiable</A><BR>
				<A HREF="E417.html">417 - Expectation failed</A></P> 
			 <P><B>5?? errors</B></P> 
			 <P>Errors with a code in the range 500-599 occur where your Web
				server reports an internal error in its operations.</P> 
			 <P><A HREF="E500.html">500 - Internal server error</A><BR>
				<A HREF="E501.html">501 - Not implemented</A><BR> <A HREF="E502.html">502 - Bad
				gateway</A><BR> <A HREF="E503.html">503 - Service unavailable</A><BR>
				<A HREF="E504.html">504 - Gateway timeout</A><BR> <A HREF="E505.html">505 -
				HTTP version not supported</A> </P></TD> 
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